Electrical musical instrument



Nov. 10, 1970 U. A. ILDE 3,539,101

ELECTRICAL MUSICAL INSTRUMENT Filed July 7, 1967 3 Sheets-Sheet 1MICROPHONE LOUD SPEAKER DETECT PRODUCE PITCH l PITCH I AND LEVEL ANDLEVEL U [550 PREAMPLIFIERS 352 30| v 1 353 MAGNETIC I 5.55

553 READ ssll s54 HEADS I l /56l 554 MIXER i L LEGEND FIG. 2A. FIG.2B.

INVENTOR Ursula A. Milde Nov. 10, 1970 U, A. MILDE 3,539,701

ELECTRICAL MUSICAL INSTRUMENT Filed July 7, 1967 3 Sheets-Sheet 2AUTOMATIC MANUAL 1) BANDPASS THRESHOLD 282 283 284 FILTERS GATES 2oI--22s I 299 II a o my W; XX KKX f j 280 288 :-235 /i 2 b I 287 V f 289..

r xx f2 216 T l f 1 V I I 252 -277 souuo I I I I SOURCE loI I I I I I II k 402 I I MANUAL PITCH (KEY) I I KEYBOARD CONTROL I PREAMPLIFIER I I II I i i I I 225 250; L

JIL a I 7/ I w f25 J I V0-o2 27s LEVEL w w DETECTOR I LEVELPOTENTIOMETER 294 INVENTOR FIG.2A.

3 Ursula A.Milde Nov. 10, 1-970 u. A. MILDE ELECTRICAL MUSICALINSTRUMENT 3 Sheets-Sheet 3 Filed July 7, 1967 TIMING MARK (RECORDED ONTRACK) e m m C M E W H w m c m 8 In T A N 4 lm M T H M m 2 P U IGI u U sr U w: I rl lllllil w m M w A E MM 9 E w E M, R v h W R L T C I M 7 V BR E W M D 45 W I H O E W E HER N 3 w 3 w H C 5 X I! I L T I! U N a n 4 Hm How .3 3 M W 3 A A H w a n r G w m H w M G s e m m m r p. a .30.. L|3I 0 PO r W 4 5 M... H s g G a m C m m lu B s a. m {2 w G 5 l w J J F s AM 1 J United States Patent O U.S. Cl. 84-118 16 Claims ABSTRACT OF THEDISCLOSURE A method and apparatus for electrically generating musicalsounds. The invention consists of a device for detecting the pitch andlevel of an input audio signal and a further device for generating thenote of any recorded instrument of corresponding pitch and level. Thedetecting device consists of a plurality of parallelly connectedbandpass filters which drive an identical number of adjustable thresholdgates. The output of the threshold gates is used to select a note ofparticular pitch at the generator. The detecting device further consistsof a level detector which controls the output level of the generator.The generator consists of a magnetic recording drum upon which arerecorded two tracks for every note it is able to produce, one for thetransient or attack characteristic of the note and the other for thesteady state. The generator receives instructions as to the pitch of thenote to be played, plays first the transient, then the steady state at alevel prescribed by the level detector.

BACKGROUND OF THE INVENTION The present invention relates to a methodand apparatus for generating musical sounds, more particularly, thesound of any desired instrument.

Many devices have been invented in past which simulate the sounds of thestandard musical instruments, notably that of the pipe organ. A few haveused the technique of recording the audio signal of every note of themusical scale on a magnetic drum or disc, and, at the desired moment ofplay, reading the note into an amplifier and, in turn, a loudspeaker.This latter system has the advantage that it may literally reproduce thesounds of the best instruments in the world. If the generation of aviolin sound is desired, for example, a Stradivarius instrument might beused in the original drum or disc recording. 7

This system as described has never been practical for the reason thatonly the steady state sound of any instrument could be recorded. Animportant characteristic of the tone of any musical instrument is thesound it makes when the tone is begun. This characteristic, called theattack, is a transient which varies from instrument to instrument, fromnote to note. It is an extremely complicated addition of harmonics withtime varying amplitudes, which, for all practical purposes, defiesdirect generation.

The present invention additionally relates to a method and apparatus forplaying a device which generates musical sounds, more particularly forreceiving musical sounds of one instrument, detecting level and pitch,and controlling the production of sounds, by the generator, of anothermusical instrument.

There has long been a need, in the musical circles, for a device whichwould enable the player of one instrument to play another. Musicianshave learned to play a plurality of instruments in the past, but haveinvariably found that best proficiency came with specialization. Variousmechanical devices have been invented to bring similarity between theoperation of instruments, however, none have used the actual sound ofone instrument to choose the notes of another.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a musical signal generator of the recording type which alsoreproduces the attack characteristic of the instrument recorded.

It is a further object of the present invention to provide method andapparatus for the generation of musical sounds of one instrument inaccordance with the notes played on another.

These and other objects which will hereafter become apparent areachieved by a device consisting of a number of bandpass filters eachadjusted to pass only the frequencies in the immediate vicinity of onenote of the well tempered scale, a corresponding number of thresholdlevel detectors each connected to a bandpass filter for determining whena note has been played, and a magnetic recording drum, having two tracksper note, one track capable of reproducing the attack characteristic,the other, the steady state of any musical instrument, operativelyconnected to the threshold detectors so that first the attack and thenthe steady state of any note is generated in response to a signaltherefrom. The device is thus capable of hearing what note is sung orplayed by the musician, converting this information into signalsdenoting the pitch and level of the sound heard, and reproducing thesound of any desired instrument, in accordance with these signals, atthe same pitch and level.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing theoverall system which forms the basis of the instant invention.

FIG. 2A is a schematic diagram showing the pitch and level detector ofthe preferred embodiment of the instant invention.

FIG. 2B is a schematic diagram showing the musical signal generatoraccording to the preferred embodiment of the present invention.

FIG. 3 is a schematic diagram showing one type of magnetic head controlswitch that may be used with the signal generator of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 of the drawings is ablock representation of the apparatus and method that forms the basis ofthe invention: apparatus and method wherein musical sounds of oneinstrument may be converted to the musical sounds of another. Soundwaves of any pitch, level and quality impinge on microphone where theyare converted to corresponding electrical oscillations. The pitch of thefundamental note, as well as the level or intensity of the tone isisolated in electronic device 200 and the information transmitted to amusical tone generator 300. The generator 300 is capable of producingthe electrical signal facsimile of the musical note of any given musicalinstrument, with the possible exception of the human voice, at anintensity corresponding to that detected by the device 200. Thiselectrical signal is then passed to a loudspeaker 600.

It will be appreciated that the system shown in FIG. 1 is neitherlimited to a single pitch and level detector nor a single producer. Onedetector may be used, for example to feed a number of electronic toneproducers each generating the sounds of a different musical instrument.Likewise a single tone producer generating, say, the sounds of an organ,may be fed by various detectors adjusted to detect the pitch and levelof various other instruments to provide a number of organ voices orsimultaneous lines of music.

A complex system is readily contemplated whereby any number of detectorsmay be switched into service to control any desired number of tonegenerators. As will be explained in more detail below, the tonegenerators need not necessarily produce sound at the pitch emitted bythe source instrument but might be further switchable to permit theproduction of music in any desired key.

FIG. 2A depicts the preferred embodiment for detecting pitch and level.Electrical oscillations in the audio range originate at the sound source101 which may be a microphone; a magnetic tape, magnetic drum,phonograph or motion picture reproducing head; a ratio or televisionaudio output or any similar device. These oscillations may be amplifiedif necessary by introducing a preamplifier 102 into the circuit.

The electrical oscillations are then fed to a number of bandpass filters201 to 225 of conventional design arranged in parallel. These filtersare each tuned to a note in the welltempered scale with a Q sufficientto distinguish notes a half-tone apart. Since the welltempered scaleconsists of thirteen notes in an octave, each, as is well known, definedby a particular frequency, a pitch detector with the normal musicalinstrument and singing voice range of two octaves must comprisetwenty-five such filters. If the musical sounds to be detected are tooccur in the lower musical registers it might be necessary to insert afrequency doubler in the circuit after the preamplifier and to set allbandpass filters to a frequency an octave higher. This technique willovercome the practical difi'iculties of obtaining the necessary Q wherethe difference of a half-tone is but a few cycles per second.

The output of each bandpass filter is connected to the input of aseparate adjustable threshold gate. Twenty-five threshold gates 226-250have been indicated for this purpose in the diagram. The object of thethreshold gates, which are of conventional design, is to produce avoltage at the output if the input voltage exceeds a given value. If theinput voltage is less than the threshold the output is either at groundor at least at some other potential. It is common in the art to call theformer output a 1, the latter a this nomenclature will hereinafter beused. The threshold gate is commonly called a Schmitt trigger.

The circle in the center of blocks in FIG. 2A, as well as FIG. 2B, fromwhich emanate the short hash marks is intended to indicate that thedevice represented by the block is subject to the manual adjustment ofsome parameter. The threshold voltage of the threshold gates must herebe adjustable so as to cause a 1 only when the fundamental of any notehas passed through the bandpass filter. Harmonics as well as unwantedbackground may, in this simple manner, be excluded from detection. Sincethe amplitude range of any given note varies from instrument toinstrument, and of any given instrument even from note to note, the useof the detector to distinguish notes of more than one instrumentnecessitates the availability of manual adjustment.

The outputs 1 or 0 of the parallel threshold gates may be directlyconnected to the musical signal generator shown in FIG. 2B and discussedin detail below. In this case they would each be simply connected to aseparate magnetic head control switch; if there be 25 threshold gates,to 25 control switchesTwo further features are shown in FIG. 2A,however, which may be inserted intermediate between the threshold gatesand the control switches. The first permits the manual operation of thesignal generator by keyboard, and the second the selection of musicalkey.

Since the musical signal generator is capable of producing the sounds ofpractically any musical instrument, it permits the musician toconveniently play all instruments without laboriously learning theirtechnique. If the musician can operate a keyboard, as for example, apiano keyboard, he can operate the musical instrument which the musicalsignal generator is designed to imitate. Singlepole, single-throwswitches 251-275 biased with a mechanical spring or some other device tohold them nor-- mally open, serve, when manually depressed, to provide a1 signal to the magnetic head control switch of the musical signalgenerator. When open they provide a 0. These switches are physically inthe form of push buttons, piano keys, or any other configuration whichis easy to play.

One terminal or circuit point of the switches 251-275 is connected to asource of voltage V, which potentially represents a 1. The otherterminal or circuit point is connected through switch 276 to themagnetic head control switch of the musical signal generator. Multiplepole, double throw switch 276 permits setting the apparatus toautomatic," whereby the pitch and level detector are connected into thecircuit, or to manual. In the manual setting terminal switches 251 to275 as well as a level potentiometer are connected to the musical signalgenerator. It will be appreciated that the 1 signal, which is to begenerated by closing the switches 251-275, can be represented by anyother potential as well, including a negative potential or even ground.

The output of either the pitch detector (automatic setting) or themanual keyboard (manual setting) may then either be connected directlyto the magnetic head control switch of the musical signal generator orto a key control switch 277, as shown in FIG. 2A. The key control switchis simply a multiple pole (one per input note channel) multiple throw(one per output note key) switch which connects all input note channelsto a number of possible magnetic head control switches. This switchenables the operator to play the input in one key, say C major, andproduce signals and, of course, by loudspeaker, sounds in any other. Ifthe keyboard is used, this feature would permit an operator to alwaysplay in his most accustomed key while choosing any other. If the pitchand level detector is used to detect, for example, voice sounds from amicrophone, the singer need only sing in his most comfortable register.

The switch 277 comprises a number of input circuits 290 which each maybe selectively connected to a number of output circuits 281 to 289. Theoutput circuits pass through a cable 299 to the musical signal generatorwhere each is connected to a magnetic head switch. The output circuitscan thus be connected with any desired magnetic head switch to give thedesired key; the simplest and most obvious format would be a connectionof the input notes so as to selectively generate notes up to, say 4 halfnotes below, and 4 half notes above the note played as well as the noteitself.

The sound source generated signal is also connected to a level detector291 which produces a D.C. voltage output in proportion to the A.C.voltage input. Any known technique such as integration may be used toobtain this result. The D.C. output is passed through switch 276 on line298 to the musical signal generator where it is used to control thelevel of the output as described in detail below.

In the event that the operator wishes to control the output levelmanually, either switch 276 or a separately provided switch may be usedto disconnect the level detector and connect a potentiometer 294. Thispotentiometer permits setting the D.C. voltage on line 298, at will,anywhere from zero to V as shown in FIG. 2A. The signal generationmechanism thus normally operates to produce higher musical volume thegreater the voltage.

FIG. 2B, showing the preferred embodiment of the musical signalgenerator, will now be described. This device employs a magnetic drum351 of conventional design having two tracks for every note to beproduced. The steady state tone of a musical instrument is recordedcompletely around one track at a constant level so that the drum mayturn more than one complete revolution without any consequent break inthe signal. This requirement necessitates more than the mere recordingof a note on one circumference of the drum; the tail of a singlecircumference must be placed in phase with the head of the recordedsignal so that no audible change in the tone occurs at the joinder ofhead and tail. The phase may be adjusted by slightly increasing ordecreasing the frequency of the entire recorded signal, a process bestcarried out by adjusting the speed of the recording from which the drumrecording is made.

The second track for each note recorder on the magnetic drum carries thestarting transient or attack characteristic of the musical instrumentrepresented. This characteristic is recorded in one circumference of thedrum beginning in the case of every note at a certain reference linedrawn in the axial direction along the face of the drum. Since the timelength of the attack characteristic varies from instrument to instrumentand even with one instrument from note to note it will be necessaryeither to adjust the circumference of the drum or the speed of the drumsrotation so that the attack transients are completely damped for all thenotes in exactly one revolution.

The magnetic drum shown in the diagram is provided with forty-nine dualtone tracks, twelve per octave for four octaves and an additional onemaking the highest note four octaves above the lowest. The drum has asingle additional timing track on which, precisely where the trackcrosses the reference line, is recorded a timing mark or blip.Ninety-nine magnetic recording heads 352 to 450 are arranged in an axialline, one per track, to read the tracks described above. The tone trackheads are connected directly to the magnetic head control switches 302-350, of which there are also forty-nine, one per dual tone track, or inother words, one for every two heads. The timing track magnetic head 352is connected through a preamplifier 301 to each of the magnetic headcontrol switches. The magnetic heads 352-450, the preamplifier 301 andthe control switches 302-350 constitute means, according to thisembodiment of the present invention, for reading first the attacktransient and then the steady state characteristic of a desired musicalnote or notes from the plurality of recorded notes.

The reference line described above need not, of course, be a physicalline drawn on the magnetic drum. Its purpose is merely to insure thatthe start of the attack characteristics are all aligned with the timingmark as recorded on their respective tracks. It may be helpful duringdrum recording to actually have a visible line; however, this depends onthe manufacturing processes used.

The magnetic head control switches 302 to 350 will be further describedbelow in connection with FIG. '3 and the discussion of operation of themusical signal generator. Sufiice it now to say that the output of eachis the composite of the transient and the steady state recorded signals;that is, a single musical note. Each control switch is connected to itsown level preamplifier 451 to 499 wherein the signal is amplified anadjustable amount. Not shown but useful is an adjustable note endcontrol connected in each channel and to the pitch and level detectorwhich anticipates the end of the note and drops the volume gradually,not abruptly as would be the case with the presently shown apparatus.

To the level preamplifiers or note end control devices may be attachedother commonly known devices 500 to 548, such as the echo, vibrato ortremolo generators. These devices should be individually manuallyadjustable in all the significant parameters; namely period, amplitude,attack and damping transients, etc.., or attached to some device whichdetects these parameters in the input to the pitch and level detectorfor automatic control of same. The various channels are finally combinedin a mixer 562, and fed through a final amplifier 549 which includes thelevel control. This amplifier 549 responds to the voltage on line 298 toproduce an output signal of corresponding amplitude. This controlfunction is most easily accomplished by using the voltage from line 2985 to bias the first stage of amplification. The lower the bias the lowerthe output signal from that particular stage.

The final signal emerging from the amplifier 549 is fed to a sound sink,which can be a loudspeaker, magnetic tape or phonograph recording head,motion picture sound recording head or the like.

Turning now to FIG. 3, which illustrates one type of magnetic headcontrol switch that may be used with the present invention, it isnecessary to briefly state the modus operandi of the musical signalgenerator. The two recording heads for any note constantly read thetransient as well as steady state tone tracks and pass these to themagnetic head control switches. As soon as the control switch receives a1 input from the pitch detector described in connection with FIG. 2A:

(a) it Waits until it receives the next timing signal from timing trackhead 352 and preamplifier 30 1;

(b) upon receipt of the first timing signal it connects the transientrecording head, through a preamplifier, to the output;

(0) upon receipt of the second timing signal (denoting one completerevolution of the drum), it disconnects the transient recording head andconnects the steady state recording head, through a preamplifier, to theoutput;

(d) it maintains the final connection mentioned above, the receipt offurther timing signals notwithstanding, until the input from the pitchdetector returns to 0. While the input is 0, of course, both recordingheads remain disconnected from the output.

It is therefore seen that first the transient, then the steady state isread from the recording of any given note. There is a short waitingperiod between the playing of a note and the production of same untilthe magnetic heads next cross the reference line but, as the length ofthe attack characteristic is short, usually in the neighborhood ofsecond, this period will not be noticeable. It is interesting to note inthis regard that these instruments with the longest attackcharacteristic are just those instruments that must be played theslowest and for which, therefore, the waiting period will be lessnoticeable. Compare, for example, the bass (slow, long characteristic)and the violin (fast, short characteristic).

FIG. 3 depicts two flip-flops 555 and 557, capable of being triggered bypositive going pulses, AND gates 553 and 558, inverter 554,differentiator 556, mixer 561 and controllable preamplifiers 559 and560. The input 551 from the pitch detector, normally 0 but in the 1state when a note is to be played, passes through AND gate 553 uponcoincidence with a timing signal on line 550 from magnetic head 352 andpreamplifier 301. Since the flip-flop 555 was held in its reset state Rby the positive signal from inverter 554, it will change to the setstate S on the occurrence of the 1 and the first timing mark. The ANDgate 558 will then pass the set output signal to preamplifier 559 toenable the transient signal from magnetic head 353 to pass through mixer561 to the output line 552. The other input to AND gate 558 will be 1since flip-flop 557 has been constrained to start in the reset state bya signal from inverter 554. The preamplifiers 559 and 560 operate assignal gates, permitting the recording signal to pass from the magneticheads 353 and 354 to mixer 561 if and only if a 1 appears on therespective enable inputs.

When the second timing mark is read the signal is passed through ANDgate 553 to reset flip-flop 555. The set output signal ceases and therecorded signal from head 353 is halted at preamplifier 559. The resenceof a sudden increase in voltage at the reset output of flip-flop 555,however, causes the difi'erentiator 556 to produce an output pulsesetting flip-flop 557 and enabling the recorded signal from the steadystate magnetic head 354. This signal is also passed through the mixer561 to the output line 552.

Flip-flop 557 will remain in the set position until the input on line551 changes from a 1 to a 0. The inverter 554 will then reset bothflip-flops and hold them there until the note, which the particularmagnetic head control switch controls, is played again. It will be notedthat flip-flop 555 oscillates between the set and reset conditions Whilethe note is played but is only functional in the control switch whileflip-flop 557 remains reset.

Although this invention has been described with reference to a specificillustrative embodiment thereof, it will be understood that variousmodifications, elaborations and alterations will occur to those skilledin the art which do not depart from the essential spirit of theinvention.

What is claimed is:

1. An electrical musical instrument comprising, in combination (a) firstinput means for producing at least one signal determinative of the pitchof a musical note to be played;

(b) recording means having both the attack and the steady statecharacteristics of a plurality of musical notes recorded thereon;

() reading means, connected to said first input means,

for reading from said recording means first the attack, then the steadystate characteristic, of said note to be played upon receipt of saidsignal from said first input means.

2. The electrical musical instrument defined in claim 1, wherein saidfirst input means comprises a source of electrical signalsrepresentative of musical sound and means, connected to said signalsource, for producing said at least one signal determinative of thepitch of the musical notes of said musical sound.

3. The electrical musical instrument defined in claim 2, wherein saidsignal producing means comprises a plurality of frequency filtersconnected to said signal source.

4. The electrical musical instrument defined in claim 3, wherein saidfrequency filters are connected in parallel and said signal producingmeans further includes a plurality of threshold gates, connected to saidfrequency filters, for producing an output only if the output of afrequency filter exceeds given level.

5. The electrical musical instrument defined in claim 1 wherein saidfirst input means comprises a voltage source, a plurality of circuitpoints and a plurality of switches each of which connects said voltagesource to one of said circuit points.

6. The electrical musical instrument defined in claim 1 wherein saidrecording means is a rotating drum having a plurality of recordingtracks wherein on one of said tracks is recorded at least one timingmark; on half the rest of said tracks are recorded the attackcharacteristics of said plurality of musical notes, one characteristicrecorded on each one of said tracks; and on the other half of said restof said tracks are recorded the steady state characteristics of saidplurality of musical notes, one characteristic recorded on each one ofsaid tracks.

7. The electrical musical instrument defined in claim 6, wherein saidrecording means is a magnetic recording means.

8. The electrical musical instrument defined in claim 6, wherein saidreading means includes a plurality of read heads, each of said headsbeing arranged to read one of said recording tracks, and wherein saidreading means further includes means responsive to said first inputmeans for connecting selected ones of said read heads to an output.

9. The electrical musical instrument defined in claim 8, wherein saidconnecting means is connected to a read head arranged to read said trackhaving said timing mark recorded thereon, and wherein said connectingmeans is operative, responsive to said first input means,

(1) to connect to said output, in response to a first reading of saidtiming mark, the read head arranged to read the attack characteristic ofsaid note to be played;

(2) to connect to said output, in response to a further reading of saidtiming mark, the read head arranged to read the steady statecharacteristic of said note to be played; and

(3) to disconnect from said output, responsive to said first inputmeans, the read head arranged to read the steady state characteristic ofsaid note to be played.

10. The electrical musical instrument defined in claim 1, furthercomprising amplifier means connected to said reading means.

11. The electrical musical instrument defined in claim 10, furthercomprising loudspeaker means connected to said amplifier means.

12. The electrical musical instrument defined in claim 1, furthercomprising second input means for producing a signal determinative ofthe level of said note to be played, and output means, connected to saidreading means and to said second input means, for producing an outputsignal representative of said note to be played, the level of which isdependent on the signal received from said second input means.

13. The electrical musical instrument defined in claim 12 wherein saidsecond input means comprises a voltage source, a circuit point and avariable voltage divider connecting said source to said circuit point.

14. The electrical musical instrument defined in claim 12, wherein saidsecond input means comprises a source of electrical signalsrepresentative of musical sound and a level detector, connected thereto,for producing an output which depends upon the level of said musicalsound.

15. The electrical musical instrument defined in claim 14, wherein saidelectrical signal source produces a signal which is an analogrepresentation of said musical sound and said level detector produces anoutput which depends upon the average level of said signal produced bysaid signal source.

16. Apparatus comprising, in combination:

(a) a signal source, said signal being representative of at least onefirst musical note;

(b) means connected to said source, for detecting the pitch of said atleast one first note; and

(c) means, connected to said pitch detecting means, for producing atleast one second musical note, the pitch of which is dependent on thepitch of at least one of said at least one first note, said producingmeans including arecord medium having a plurality of tracks, said trackshaving the attack characteristic and the steady state characteristicrepresentative of a plurality of musical notes recorded thereon, andsaid producing means further including reading means for reading firstthe attack characteristic and then the steady state characteristic of atleast one selected recorded musical note in response to said detectingmeans, said at least one selected note being said at least one secondmusical note.

References Cited UNITED STATES PATENTS Dorf 84-*1.01 X

PAUL L. GENSLER, Primary Examiner US. Cl. X.R. 84--1.26

